LED stands for “Light Emitting Diode” and called Swedish for LED. It is a kind of semiconductor that when sending electric current through it emits light. LEDs have been with us a long time and has been used in electronic appliances, cars and all sorts of applications. A few years ago it began to appear as products used as standard bulbs.
In today’s products, there are a few different types of diodes often seen:
- SMD diodes SMD shortening. The most common variant that looks like a small square plate with a colored circle in the middle.
- COB stands for Chip On Board and is a diode solution that consists of a lot of small diodes. Often used in spotlights and floodlights.
- Filament lamps are a type of solution where it sits rows of small LEDs inside a dye which makes it look like old-fashioned carbon filament filaments when they are on.
- Radial diodes are the classic LEDs.
The luminous flux emitted shall in accordance with Directive EU measured in units of lumens and should go to find to clearly be able to compare different products.
The light flux indicates the total flow of light in all directions as the lamp emits. A lamp having a narrow beam such as a spotlight will be perceived as more intense on a surface than an omnidirectional light. It can therefore be e.g. a desk lamp with a lower light output with a smaller beam angle than an equivalent incandescent lamp.
It is difficult to measure the light output in lumens, measured in rather light output or brightness.
Light effect or illuminance stated in lux (lx) and describes how many lumens per square meter that hits a surface. One can measure the flow of light using a luxmeter.
How much of the light flux that hits a surface depends on e.g.
- The distance from the light source to the surface
- Light source beam angle
- If anything is between the light source and the surface
There are apps to the mobile phone to measure an approximate value of the light output in Lux.
Brightness is measured in units of Candelas (cd) and it is possible to deduce the flow of light according to the brightness and light source characteristics. Some light sources such as flashlights often have indication of how the brightness of the CD’s instead of ch.